The general objective of this research is to study fetal maturation and its relationship to initiation of parturition. Of particular concern is the maturation of the fetal hypothalamus as it relates to the increased fetal adrenal activity associated with parturition. Fetal hypothalamic content of CRF will be measured at various stages of pregnancy and the ability of the fetal pituitary to secrete ACTH will be similarly examined. The efficacy of an ACTH releasing substance, lysine-vasopressin, in stimulating fetal adrenal activity and initiating premature parturtion will be examined. In vivo studies related to fetal maturation will utilize restriction of blood flow to the late pregnant sheep uterus. The response (bochemical and hormonal) of the fetus to the effects of this restricted blood flow, i.e., reduced nutrient supply and accumulation of waste products, will be monitored to determine whether and how the fetus responds to stresses. A further objective is the elucidation of the mechanism by which the increased fetal corticoids may cause the initiation of parturition. The model of induced parturition using glucocorticoids in cattle and sheep will be studied using HCG and anti-PG compounds (indomethacin) as potential parturition blocking agents. Since these two species have different progesterone sources (cow-CL and sheep-placenta) this should provide knowledge concerning whether or not there are similar mechanisms for the parturition process in different species and how prostaglandins may be involved in this process.